It is well known that isocyanates may be added to alkyd resins to improve both the curing behavior and the properties of the cured coating. The preparation and use of urethane oils of this type are extensively discussed at pages 468 to 477 of Polyurethanes: Chemistry and Technology, Volume II, Technology, Saunders and Frisch, Interscience 1964. It is also known that aliphatic isocyanates impart superior light stability (resistance to yellowing, particularly on exposure to sunlight) as compared to aromatic isocyanates. A class of isocyanates which has found particular favor for coating applications are the biuret containing aliphatic or cycloaliphatic isocyanates especially the tris (isocyanato alkane) biurets such as those disclosed in U.S. Pat. Nos. 3,124,605 and 3,201,372. It has been found desirable to add such isocyanates to alkyd resin systems containing aliphatic solvents such as those used in the auto refinishing industry. Unfortunately, while these biuret isocyanates including the popular tris (isocyanato alkane) biurets exhibit some degree of compatibility with the alkyd resins themselves, they display a high degree of incompatibility with the aliphatic solvents normally used in such systems. Since these solvents are both effective and economical in such systems, it was felt that the compatibility of the aliphatic biuret isocyanates would have to be improved if they were to find practical utility in these systems.